Storyline- Next button to become available after visiting another slide

Hi Jill - Great question and it is confusing, so let's see if I can explain.

When visiting the slide again, the timeline is re-starting, even with the saved states. So, when you have a trigger to change the state of the Next button when the other buttons are visited, it happens in the same instant you are viewing your other slide/layer. When you go back to that slide, the timeline starts - which goes back to your disable the next button trigger. Now, variables cross slides and are not dependent on being ON that slide when they happen.

Your third trigger to have the conditions attached is what is really working here. 

Way to get that figured out though :) Hope I didn't confuse you more.